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Homeostasis Flashcards

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1
Q

What are the behavioural mechanisms that allow endotherms to maintain body temperature?

A

What are the behavioural mechanisms that allow endotherms to maintain body temperature:
-When too hot = Astivation (hibernation in the summer to avoid heat stress)
-When too cold = hibernation (conserves heat and energy)

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2
Q

Physiological mechanisms that allow endotherms to maintain body temperature when too hot?

A

Physiological mechanisms that allow endotherms to maintain body temperature when too hot:
Pilli muscles (hair erector muscles) -> less heat trapped
-Vasolidation -> dilation of arterioles -> blood close to surface of skin -> skin flushes and body cools due to radiation
-No shivering
-Sweating -> heat lost through evaporation

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3
Q

Physiological mechanisms that allow endotherms to maintain body temperature when too cold?

A

Physiological mechanisms that allow endotherms to maintain body temperature when too cold:
-Shivering -> rapid skeletal muscle contraction -> generates metabolic heat
-Vasoconstriction - constriction of arterioles - blood not close to surface
-Pilli hair muscles contracts -> more heat trapped
-No sweat produced

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4
Q

What is homeostasis?

A

Homeostasis is the body maintaining a dynamic equillibrium to maintain conditions

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5
Q

Feedback systems within the body

A

-Negative feedbacks: change detected by sensory receptors - effectors work to reverse change and restore conditions
-Positive feedbacks: change in internal environment detected by sensory receptors = effectors stimulated to enhance response

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6
Q

Two control centres involved in controlling thermoregulation

A

Two control centres involved in controlling thermoregulation:
-Heat loss centre - when temp increases - impulses sent through autonomic motor neurones to effectors
-Heat gain centre - when temp low

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7
Q

Main metabolic waste excreted by mammals

A

Main metabolic waste excreted by mammals:
-Carbon dioxide - eg from cellular respiration
-Bile pigments - from haemoglobin breakdown from old rbc - excreted in bile from liver into small intestine via gall bladder and bile duct - colours the faeces
-Nitrogenous waste products (urea) - breakdown of amino acids by liver

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8
Q

What is the vein which supplies liver with the blood?

A

The hepatic portal vein supplies the liver with blood - upto 75%

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9
Q

Liver cells

A

Liver cells (hepatocytes) - large nuclei, prominent golgi, lots of mitochrondria, divide and replicate (means liver can regenerate fast)

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10
Q

Blood from the hepatic artery and hepatic portal vein into the liver

A

Blood from hepatic artery and hepatic portal vein is mixed in spaces (sinusoids) surrounded by hepatocytes - mixing increases oxygen content, supplying hepatocytes with oxygen for their needs -

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11
Q

Sinusoids of the liver

A

Sinusoids - spaces where blood from hepatic artery and vein is mixed - contains Kupffer cells (acts as the resident macrophages of the liver)

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12
Q

Role of the hepatocytes of the liver

A

Hepatocytes - liver cells - secrete bile fromthe breakdown of the blood into spaces called canaliculi, and from these the bile drains in to the bile ductules which take it to the gall bladder

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13
Q

Functions of the liver

A

Functions of the liver include:
-Carbohydrate metabolism - hepatocytes stimulated to convert glucose to glycogen or convert it back to glucose
-Deamination of excess amino acids

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14
Q

Deamination of excess amino acids in the liver

A

Deamination = removal of an amine group from a molecule - as body cannot store proteins or amino acids - excess ingested would be extreted and wasted if not for deamination by hepatocytes - which deaminate the amino acids

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15
Q

Transamination by hepatocytes

A

Transamination by hepatocytes = conversion of one amino acid into another - importance as diet doesnt always contain required balance of amino acids

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16
Q

Process of deamination by hepatocytes in the lvier

A

Deamination = remove amino group and converting it to ammonia (toxic) - so converted to urea = toxic in high conc but not in normal conc - urea then excreted by kidneys - remainder of the amino acid fed into cellular respiration

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17
Q

What is the ornithine cycle?

A

The ornithin cycle - ammonia producted in the deamination of proteins converted into urea by enzyme controlled reactions in this cycle

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18
Q

Detoxification in the liver

A

Detoxification occurs in the liver - breakdown of toxins and made harmless - eg catalse splitting hydrogen peroxide into oxygen and water
-Or ethanol detoxification into ethanal which can be converted to ethanoate and used in respiration

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19
Q

What are the kidneys?

A

The kidneys are red-brown organs attached to the back of the abdominal cavity,surrounded by thick protective tissue

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20
Q

Describe the kidne structure?

A

-Made up of nephrons (filtering units)
-Cortext (dark outerlayer, soite of blood filtration
-Medulla (lighter area inside cortex, contains nephron tubules which make kidneys collecting ducts)
-Pelvis (collectsw urine)
-Ureter (tube that connects kidney to bladder)
-Bladder (holds urine)
-Urethra (tube that allows urine excretion)

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21
Q

Role of the ureter in the kidneys?

A

Ureter = tube which connects kidney to the bladder

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22
Q

Role of the cortex and the medulla in the kidneys?

A

Cortex = High density of capillaries as it is the site of blood filtration
Medulla = within the cortex, contains nephron tubules which make the kidneys collecting ducts

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23
Q

Role of the urethra in the kidneys?

A

Urethra = tube which allows for urine in the bladder to be excreted

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24
Q

What are nephrons?

A

Nephrons - where blood is filtered in the kidneys - removes nitrogenous waste and balances mineral ions and water levels in the blood
-about 3cm long, over 1 mil per kidney - provides body with kilometers of water, glucose, salt reabsorption

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25
Q

Structures found within the nephron?

A

Structures found within the nephron:
-Bowermans Capsule
-Glomerulus
-Proximal convoluted tubule
-Loop of henle
-Distal convulated tubule
-Collecting duct

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26
Q

Bowmans capsule found within the kidneys

A

Bowermans capsule = a cup shaped structure containing the glomerulus where ultrafiltration takes place (filtering small molecules and ions out blood but keeping large molecules ie proteins)

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27
Q

What are the three filtering systems in the Bowman’s Capsule?

A

Three filtering systems in the Bowman’s Capsule that helps prevent cells and large molecules leaving out the blood:
-Narrow gaps (fenestrations) between endothelium cells in capillaries
-Basement membrane (mesh of collagen around glomerolus)
-Podocytes (epithelial cells of the capsule that have finger-like pojections, which form filtration slits)

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28
Q

Role of the glomerulus?

A

Glomerulus: a tangle of capillaries in which the pressure forces all solutes in the blood plasma to be forced through the capillary walls. This includes ions, amino acids, glucose, urea, water. Proteins and erythrocytes do not pass through as they are too large.

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29
Q

Proximal convulated tube within the kidneys

A

Proximal Convoluted Tubule: First coiled region of the tubule, where products needed in the blood (ions, glucose, amino acids etc) are reabsorbed into the blood.

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30
Q

Loop of henle within the kidneys

A

Loop of Henle: Establishing a water potential gradient (

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31
Q

Distal convoluted tubule within the kidneys

A

Distal Convoluted Tubule: Second coiled region of the tubule, where osmosis and diffusion of solutes occurs in order to fine tune the water potential and pH of the blood. Antidiuretic Hormone (ADH) affects the permeability of the distal convoluted tubule.

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32
Q

Collecting duct within the kidneys

A

Collecting Duct: Urine travels through the collecting duct down to the pelvis. More fine tuning occurs, as ADH creates aquaporins to allow the exit of excess water.

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33
Q

Ultrafiltration in the glomerulus and Bowmans capsule

A

Ultrafiltration in the glomerulus and Bowmans capsule:
The glomerulus is supplied with blood from a comparatively wide afferent renal artery, but leaves through a narrower efferent renal artery. This means the blood in the glomerulus is under very high pressure.
This causes the contents of the blood to be forced through the capillary wall, like a sieve, then through the basement membrane (a second ‘sieve’ made of collagen fibres and protein) into the nephron.
These sieve like structures are important as they do not allow cells, large proteins or platelets to pass into the nephron.
The cells in the wall of the bowman’s capsule contain cells called podocytes, which have extensions called pedicels wrapped around the capillaries meaning any cells, large proteins or platelets which leave the capillary walls don’t enter the tubule.
Filtrates include water, amino acids, glucose, ions and importantly: urea and other nitrogenous waste products.

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34
Q

Reabsorption in the proximal convoluted tubule

A

Reabsorption in the proximal convoluted tubule:
Ultrafiltration removes nitrogenous waste, but it also removes glucose, ions and other useful substances in the plasma.
The proximal convoluted tubule are covered with microvilli, which increase the surface area available for substances to be reabsorbed.
There are many mitochondrial cells in the tubule wall, to provide the ATP required for active transport of substances back into the blood.

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35
Q

Loop of henle within the kidneys role

A

Loop of Henle = Establishing a water potential gradient (ie the water potential in the nephron filtrate becomes higher than what it is in the medulla, additional water can then be reabsorbed from the collecting duct)

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36
Q

Osmolarity definition

A

Osmolarity - concentration of a solution expressed as total number of solute particles per litre

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37
Q

Ismotic definition

A

Ismotic - to have the same osmolarity as another fluid

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38
Q

Equilibrate definition

A

Equilibrate - to bring into a state of equilibrium

39
Q

Interstital fluid

A

Interstital fluid - fluid which surrounds tissue cells

40
Q

Process of countercurrent multiplication in the loop of henle

A

Countercurrent multiplication in the loop of henle:
Before moving into the loop of henle the filtrate in the nephron is isosmotic with the blood.
Sodium and chloride ions are pumped out of the ascending limb to create a water potential gradient.
The filtrate moves down the falling limb, and water osmoses out due to the water potential gradient. The ideal gradient is 200 mOsm.
Water in the falling limb equilibrates with the interstitial fluid, by passively diffusing into the medulla. This does not change the osmolarity of the interstitial fluid.
When the filtrate moves around the loop of henle, the ideal 200 mOsm gradient is lost, so steps 3 and 4 are repeated.
After enough filtrate has passed through, the interstitial fluid at the bottom of the loop has reached a maximum osmolarity of ~1200 mOsm.

41
Q

What is osmoregulation?

A

Osmoregulation is the control of water and salt levels in a fluid

42
Q

Osmoregulation and the distal convulated tubule

A

Osmoregulation and the distal convulated tubule:
High levels of ADH are released when you are dehydrated, and cause the distal convoluted tubule walls to become more permeable to water, meaning more returns to the blood and the urine becomes more concentrated. This way we conserve water.
There are many mitochondria in the tubule cell walls, allowing salts to be actively transported out of the nephron into the blood when required. Sodium ions are actively pumped out, and chloride ions follow passively down an electrochemical gradient.

43
Q

The collecting duct in the kidneys

A

Collecting duct in the kidneys:
The urine enters the collecting duct which transports it down through the medulla to the pelvis.
The urine becomes more concentrated as it passes through the medulla, as the salty conditions created by the loop of henle mean water osmoses out down a potential gradient.
ADH also controls the permeability of the collecting duct, and creates aquaporins in the membrane which allow additional water to escape through, thus determining urine concentration and volume

44
Q

What is meant by osmoregulation?

A

Osmoregulation involves crontrolling the water potential of the blood within very narrow boundaries, regardless of the activities of the body

45
Q

Why is it important that water potential of the tissue fluid is stable?

A

Water potential of the tissue fluid has to remain stable as possible, because if water moves into or out of cells by osmosis it can cause damage and even death

46
Q

What is the amount of water lost in urine controlled by?

A

The amount of water lost in urine is controlled by ADH in a negative feedback system

47
Q

What is the role of ADH?

A

ADH is produced by the hypothalamus and secreted into the posterior pituitary gland where it is stored
-Increases permeability of the distal convulated tubule and the collecting duct to water

48
Q

What is a hypertonic cell?

A

Hypertonic = blood with low water potential - too much water leaving by osmosis - cells shrivel

49
Q

What is meant by hypotonic?

A

Hypotonic - blood with high water potential - too much water enting cell by osmosis - cells burst (lysis)

50
Q

Hypertonic negative feedback response

A

Hypertonic negative feedback response: more water reasborbed by osmosis into blood from nephron tubules -> urine more concentration -> less water lost in urine

51
Q

Hypotonic negative feedback response

A

Hypotonic negative feedback response:
-less water reabsorbed by osmosis into blood from nephron tubules -> urine more dilute -> more water lost in urine

52
Q

Describe the negative feedback response when water potential of blood increases

A

Blood water potential increases -> detected by osmoreceptors in hypothalamus -> they shrivel and stimulate hypothalamus to release less ADH -> DCT and collecting duct walls less permeable -> less water reabsorbed into blood and urine is more dilute

53
Q

Describe the negative feedback response when water potential of blood decreases

A

Water potential decreases:
Detected by osmoreceptors and stimulates hypothalamus to release more ADH into blood by posterior pituitary gland -> DCT and collecting duct walls more permeable due to increased embedded aquaporins -> more water is reabsorbed into blood and less lost in urine (more concentrated)

54
Q

What are aquaporins?

A

Aquaprorins are protein channels for water to pass through - more embedded in membrane = more water leaves DCT + collecting tubule + resbsorbed into blood

55
Q

What happens when ADH binds to cell membranes of the distal convoluted tubule (DCT)

A

ADH binds to cell membranes of DCT -> activates phosphorylate enzyme -> causes vesicles containing aquaporins to fuse with membrane and become embedded

56
Q

Why is urine used to diagnose?

A

Urine contains the breakdown of products of lots of chemicals including hormones and toxins - affected by disease = new substances show in urine ie glucose (diabetes), creatine (muscle damage)

57
Q

Traditional pregnancy testing

A

Traditional pregnancy testing: blood of mother injected into toad - if pregnant, hCG triggered egg production in the toad

58
Q

Modern pregnancy testing

A

Modern pregnancy testing:
Monoclonal antibodies are used to detect the presence of hCG hormone

59
Q

What are monoclonal antibodies?

A

Monoclonal antibodies = antibodies from a single clones of cells that are produced to target particular cells or chemicals in the body

60
Q

How are mouses used to collect monoclonal antibodies to be used for pregnancy testing?

A

Mouse injected with hCG to make appropiate antibody - Bcells removed from spleen and fused with myeloma (cancer cell) -> known as hybridoma - hybridoma replicates rapidly and antibodies are collected

61
Q

Main stages in a pregnancy test

A

Main stages in a pregnancy test:
-Wick is soaked in the first urine (highest hCG)
-Test contains monoclonal antibodies with beads attached - only binds to hCG - if pregnant, they bind forming hCG-Antibody complex (coloured bead)
-Urine carries along test
-Immbolised monoclonal antibodies arranged in line or pattern (ie +) that bind to hCG complex
-Continues to second line that binds wether hCG present or not
-Pregnant = 2 lines, not = 1 line

62
Q

What are anabolic steroids?

A

Anabolic steroids are drugs that mimic the action of testesterone and stimulates muscle growth

63
Q

How are drugs tested for using urine?

A

Urine sample used - first passed through imunoassay using monoclonal antibodies that bind to drug - then gas chromotraphy is positive

64
Q

Why might kidney failure occur?

A

Kidney failure may happen due to:
-Kidney infections
-Raised blood pressure that damages epithelial cells of bowmans capsule
-Damage from cyst pressure

65
Q

What can kidney infection/damage from high BP cause?

A

Kidney infection/damage can cause:
-Protein inurine - as bowmans capsule membrane damaged and can’t filter properly so large plasma proteins pass through
-Blood in urine due to affected filtering process

66
Q

Effect of kidney failure where conc of urea and mineral ions build up in the body

A

Effect of kidney failure where conc of urea and mineral ions build up in the body:
-Loss of electrolyte balance
-Build up of toxic urea in blood
-High blood pressure
-Weakened bones as calcium/phosphorus balance in blood lost
-Pain and stiffness in joints due to protein build in blood
-Anemia - reduced rbc

67
Q

Measuring glomerular filtration rate

A

Measuring glomerular filtration rate:
GFT widely used to indicate kidney disease = involves blood test measuring creatine level - increased creatine = kidneys not working properly

68
Q

What is creatine?

A

Creatine is a breakdown product of muscles and it is used to give an estimated glomerular filtration rate which indicates kidney damage

69
Q

Ways if treating kidney failure with dialysis

A

Treating kidney failure with dialysis:
-Haemodialysis
-Peritoneal dialysis

70
Q

What is haemodialysis?

A

Haemodialysis:
Blood flows into machine -> through partially permeable dialysis membrane (mimics bowmans capsule membrane) -> dialysis fluid on other side of machine > large proteins and blood cells cannot pass through

71
Q

How does haemodialysis prevent loss of useful substances such as glucose and some mineral ions

A

-Dialysis fluid contains normal plasma levels of glucose to ensure no net movement of glucose out of the blood as well as mineral ions
-Dialysis fluid also contains no urea to create steep conc gradient so urea leaves blood

72
Q
A
73
Q

Weakness of dialysis

A

Weaknesses of dialysis:
-Depends on diffusion down conc gradients
-takes 8 hrs and has to be repeated
-people attached to the machines many hrs a week
-carefully managed diets

74
Q

Peritoneal dialysis?

A

Peritoneal dialysis:
inside body - natural dialysis memebranes formed from abdomen lining - dialysis fluid inserted using catheter and left for several hrs

75
Q

Kidney transplant as a treatment

A

-Alternative to dialysis, can function for many years
-Risk of rejection due to differing antigens - can be overcome by matching tissue type
-Immunosupressant drugs for rest of their lives
-Donor shortage

76
Q

Why is urine useful in diagnostic tests?

A

Urine is useful in diagnostic tests because:
-Urine samples are easy to get
-Non-invasive
-Chemicals remain sometime after use - good for drug testing

77
Q

Why is urine samples divided into two step processes when testing for drugs?

A

Drug testing is split into two because:
-Passed through immunoessay involving monoclonal antibodies -> then at the same time, gas chromotography used right after -> confirms findings

78
Q

Why may false negatives appear in pregnancy tests?

A

False negatives in pregnancy tests arise due to:
-If test is done on day period is missed, woman may be pregnant but not produced enough hCG to produce strong enough coloured response -> hormone would’ve increased days later

79
Q

Why is kidney failure such a threat to life?

A

Kidney failure is such a threat to life because:
–Kidneys filter out dangerous chemicals - > these at high conc in ur blood lead to cell damage (osmotic damage)

80
Q

Flow chart to show how dialysis works

A

Flow chart to show how dialysis works:
Blood enters dialysis machine from artery -> filters through partially permeable membrane where urea filters into dialysis fluid -> dialysis fluid is moving in opposite direction

81
Q

Why does blood and dialysis fluid move in opposite directions during dialysis?

A

Countercurrent flow results in maximum concentration gradient can be achieved

82
Q

How are PCT cells adapted for reabsorption?

A

PCT cells are adapted for reabsorption in the following ways:
-Microvilli that increases surface area for reabsorption
-Plasma membranes have many pumps and transporter proteins for active transport and facillitated diffusion
-Many mitochondria to produce ATP for active transport

83
Q

Limbs of the loop of Henle

A

Limbs of the Loop of Henle:
-Descending limb (permeable to water)
-Ascending limb (impermeable to water, but sodium and chloride ion actively transported from filtrate into medulla, which raises water potential of the filtrate)

84
Q

Property of HCG that allows it to be detected in urine during pregnancy tests?

A

HCG property: B hCG has a molecular mass of less than 69,000

85
Q

A student designed an experiment to investigate the effect of temperature on the rate of glucose
diffusion through dialysis tubing.

State 3 factors that would need to be controlled in this experiment.

A

3 factors that would need to be controlled:
-Initial glucose concentration on both sides of the membrane
-Length/diameter of dialysis tubing
-Type/brand of dialysis tubing

86
Q

What is the effect of sulthiame (inhibits carbonic anhydrase) on the
reabsorption of sodium ions in the PCT?

A

-Carbonic anhydrase in the PCT catalyses reaction between carbon dioxide and water to form hydrogen carbonate which allows ion reabsorption:
-Less sodium ions enter PCT by facilliated diffusion, and no active transport of sodium ions into blood -> less ion excretion in urine

87
Q

Compare the processes occurring in the proximal and distal convoluted tubules

A

PCT and DCT comparison:
-Both involves selective reabsorption
-Both involve sodium ions
-Both involve co-transport of ions and active transport
-However, PCT involves glucose, amino acids, etc (molecules) rather than DCT which is primarily ion reabsorption (less selective)

88
Q

What is homeostasis?

A

Homeostasis is the maintenance of metabolic so to keep them functioning at regular conditions - within narrow regions in the body

89
Q

Difference between peripheral and hypothalamus receptors

A

Peripheral - found in skin - detects change in skin/responses to skin stimuli
Hypothalamus - detects change of temperature in body

90
Q

Difference between excretion and defecation

A

-Excretion = removal of metabolic waste from the body - some excretion takes place as bile produced from the breakdown of haemoglobin of old red blood cells removed in faeces
-Defecation - involves removal of undigested food and dead cells

91
Q

Adaptations of hepatocytes

A

Hepatocyte features:
-Large nuclei = suggests lots of DNA transcription
-Lots of golgi = lots of lipid and protein processing
-Many mitochondria - requires lots of ATP / they are metabolicaly active

92
Q

What happens to liver due to excess drinking

A

Excess drinking = ethanoate produced as ethanol is detoxified in the liver -> fed into pathway synthesising fatty acids - and so lipids - if there is a lot of fatty acids there is a built up of tissue

93
Q

3 Adaptations of the kidney

A

3 Adaptations of the kidney:
-Layer of fat - protects against mechanical damage
-Good blood supply - maintains concentration gradients
-Different sized blood vessels into and out of glomerolus to give high pressure for ultrafiltration

Y13 Biology (19 decks)

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